Fluid actuated load lifting and lowering mechanism



y 1949- I l. A. WEAVER 2,471,989

FLUID ACTUATED LOAD LIF TING AND LOWERING MECHANISM Filed Nov: 28, 1947 3 Sheets-Sheet l May 31, 1949. l. A. WEAVER 2,471,989

FLUID ACTUATED LOAD LIFTING AND LOWERING MECHANISM Filed NOV. 28, 1947 r 3 Sheets-Sheet 2 May 31', 1949. I. A. WEAVER 2,471,989

FLUID ACTUATED LOAD LIF'IING AND LOWERING MECHANISM Filed Nov. 28, 1 947 s Sheets-Sheet s I INVENTOR. A JFw Q. Zflmuzfl Patented May 31 1949 ii REE LOWERING MECHANISM Ira A. Weaver,--,Springfield,.Ill., assignnntoiweaver Engineering 1-00., a 'corporation df Illinois Application November 28, I947, Seiia l N;- Z88,3.81

.6 Claims. 1

' The currentinventionrelatesqto certain structural :and functional 1 improvements and :innoVatory; betterment-s in hydraulic lifting and lower- .ingaappliancesof .thetype having an upright cylinderenclosingyor encasing a companion, hollow piston or. plunger havingitsupper end closed and 'znovablelengthwisewithin thecylinder to perform :its operative service, such hollowupost containing a body oioilior other suitable liquid reaching nearlytothe: top of the piston, an;air-

pipe. extending through the bottom of the cylinder and up into the piston and terminating above .the oil+level in ;the.:latter.

When air ;.under suitable pressure is admitted throughsuch pipe and onitop of-the liquid in the piston, thev oil isfforced down out of the latter into cylinder thereby causing the piston to ascend and; perform its load: lifting or. elevating. action.

,One. of thenobj-ections to a lift ofthis general character is the "inability to stop the movement or travel of. the. piston at a definite predetermined point when :the controlling air-valve is closed,

vsuch uncertainty beingdue-to:the expansion of the air iwithinwthe :piston and to overcome-this detrimentalaction, the lower end ofthe piston 1isjclosed; andapaeking' gland surrounds the airp he...and a: valve isalso provided'at the lower end of; thepiston so. thatthe oil may pass freely from the. piston tov the cylinderwhenthe valve is open but will stop any further movement of. the piston when thevalve is closed,regardless of whether there is. anyaair pressure within the piston.

invention also .includes means to. operate such :oil control valve. through the :air inlet and contained wholly within the piston :and air inlet leading to the same.

. A further. objection to an elevating appliance ,-,of; the: type previously described is that when the oillevel islow in the piston the-air will escape through: the bottom of..the.pistonbefore the full stroke. ofrthepiston is completed, the-loadthen bein supported by air pressure rather than by the. liquid. The method, of overcoming this tactor; is hereinafter disclosed.

:In additiom assafety -feature is-provided to reventitheuair that. is! under compression in the piston'fromreachingtthe-eylinder if there is not a suificient amount of liquid. in-the piston-to-complete thezjull stroke. of the. same, and to accompush-this; desirable result. a chamber cylinder is employed. having a -shut off valve in its upper nQrtiomsuch valve being attached to the bottom of asuitably. shaped out .vwhich isisubmergedin :the; liquid andzlwhenrthe liquid is low. the weight ofxthe-oil in the cup forces: the valve on its seat and prevents any further movement; of the piston.

:Such sup is-eusnemde iimmearromeonne t d on sen it oa ,irote ziioke ndt on thetopposite end of such link1i, ..L ';r/Q sllpportinaa icounterw sht'w iohisi-aborethaonpzwhen inits uppermost movem nt-stile wei ht theme 'Sufiicieni hold-Lthe valvezzhutznotiheavy.enougnto support the eupj'that s .fi1liiof:.1iquid- .whennthe.oil level ri ll wbelow :;the 25cm) :avhich .1.=all0ws zthe .valve to ,-el,ose,.the pivoted link-z-laeingsattached rto a support ,secu-led' nearsthernppenendpfzthe piston.

' In:ordemthattthoseacquainted withsor skilled in :this: art; may: fnliy :imxierstandsthis V invention and thezx-advantages .gaccruing'cfrom its employmGIIt'JHHdZthE manneriin which-thespecifiedand other :xlesirable objects and aims; are secured, a present*-preferredsembnidimentuof -:-.the. invention hasrbeenzaillnstrateda. in. detail: in ,.the eaccompany- 1lng: drawings; in :theeseverlal wiews of which like reference nnmera'ls'havez beenemployed tofdesigmate: the. same parts.

In these drawings:

{Figure :1,-:'ior;-t,he most part, is iaalongitudinal,

, central, werti'cal .-.sect icnsrthrough the complete .,.appliance;

Figure 2.is.; atparttal plan:ofithe appl-iance with --some elements ashnwn ina'ihorizontal section;

Eieu-renuisxaffragmentary; perspectiveview of r a atop: portion :ofirthez-appanatus Eigl'll'e is a wverticalzsection on "line 4-4 of Figurez;5;is1 aihorizontal sectiomon line -:55- of rFignr'e lg-sand :Figuretfi: isamhorizozitalasectlon' on: line -6--B of Figureilpbutvoniailargerscale.

, Beferrinig to Figures-i and 4 itawi-llbe-noted 1 that theiapplianee inciudes -an extennal; upright, stationary, cylindriealioylinder i H closed at its v. bottom by a pl-ate l2' -.as'-*by Welding "at 03, a this weld being: sealstight andof-aemientstrength to withstand the n eoessary internal pressure.

Attached to;suche bottonnplate l*2;by welding, -as at" tiigissa hellowt-air-tight rectangularchambel' id -one end:of whioh -extends beyondthe side i of easing" l 'l as shownrat l6,;'p late' l 2 being also shapedsso that aportion of-itextendsbeyond the sideof casing! I,-as--showri, at-l1.

Ontop of snch extendedpart of' chamber M is welded a cylindrical, upward extended-hollow 1 boss l fl -(Figs. 51,-4- 2H1fi'f51ki012l3- l2 being-drilled through indine withvsueh'boss l+8-yth-us afiord-ing access to the-chamber I 4.

This boss l8 isiinilerhally-'-screw threaded and into itis 'screwedthedowersendof averticalpipe I9 projecting upward alongside of and parallel to casing or cylinder II, the upper end of such pipe (Fig. 1) terminating in a standard pipe fitting T29 into the side outlet of which a pipe 2| is screwed, which is supplied with an air-control valve I 2I so that compressed air may be admitted into or exhausted from chamber I4 by proper manipulation of the valve I2I, the latter being a conventional three-way valve or a two-way valve arrangement.

An upright rod 22 extends down through the T28 in pressure-sealed manner and also through the pipe I9, the upper end of such rod 22, equipped with handle I22, terminating above a suitable guide 23 welded on the side of casing or cylinder I I, the lower end of rod 22 projecting into chamber I4 with its end extending below an apertured guide or bearing 24 welded to the underside of bottom plate I2, such lower end portion of the rod having fixedly attached thereto a crank-arm 25 (Figs. 4 and 6).

On the radial center of cylinder II is an upright tube 26 projecting up through a hole in the base-plate I2 (Fig. 4) and it is securely welded to the lower side of such base-plate at 21.

Extending lengthwise through the center of such tube 26 is a rod 28 the lower terminal portion of which ends in the chamber I4 with the end extending below its bearing in guide 24 and fixedly attached to the lower end of such rod 28 is another crank-arm '29 (Figs. 4 and 6), the two ends of the companion crank-arms 25 and 29 being operatively connected together by means of an appropriate link 30 the ends of which are pivotally connected to the respective cranks by pivct-pins 3|, 3| (Fig. 6) which can turn freely in the holes in the two ends of the link the length of which between such holes being the same as that of the center-to-center distance between the two upright rods 22 and 28 whereby when rod 22 is manually turned about its longitudinal axis by its handle I22 the rod 28 is likewise revolved a like amount in the same direction.

As is illustrated, rod 22 is proportionately much smaller in circular area than the internal area of its encasing pipe I8 so that air under pressure may pass freely through pipe I9, and rod 28 is smaller in cross-sectional area than its companion tube 26 for the same reason, the upper end of such rod 28 being rigidly attached to a crankarm 32 by means of a set-screw 33 (Figs. 3 and 4).

Resting on top of the stationary tube '26 is a casting 34 (Figs. 3, 4 and 5), such portion of the casting bored out, as illustrated, to receive the tube 26 (Fig. 4) being apertured to a medium loose slide fit on the tube to facilitate assembly of the parts, casting 34 being prevented from coming off the end of tube 26 by the crank-arm 32 on the rod 28 which extends through tube 26.

This rod 28 cannot be pulled up out of tube 26 due to the presence of the crank-arm 29 on its lower end, since, as the rod 28 is lifted upward endwise through the tube 26, the crank-arm 29 secured at its lower end strikes the flange of the bushing 35 thus restraining it from being raised further. Then the upper crank 32, in the uniting of the parts, is slid down on rod 28 until it contacts the casting 34, whereupon the set-screw 33 is tightened thus retaining the elements as one assembly.

As is most clearly depicted in Figures 1, 3 and 4 just above the top end of tube 26, casting 34 has a plurality of openings 19 connected from the outside to the interior of tube 26.

In addition, casting 34 is bored vertically at 36 (Fig. 4) to receive the flanged bushing 3'! which appropriately fits such bore so that it may rotate freely therein, this bushing 31 being retained in place by the nut 38 screwed onto its lower threaded end, the upper flange of the bushing being extended on one side radially to form a crank 39 (Fig. 3), a link 48, the same length as the centers distance between the rod 28 and the bushing 31, connecting the outer ends of cranks 3'2 and 39, whereby, if the rod 28 be rotated a given amount such bushing 31 will be revolved a like amount in the same direction.

Reference has been made thus far to the encasing cylinder I I and its associated elements all of which are stationary in a vertical or longitudinal direction with reference to the axis of such cylinder.

A hollow piston 4| (Figs. 1, 4 and 5) is mounted in and coaxial with cylinder I I and is free to move up and down vertically therein.

Since the external diameter of piston 4| is substantially less than the interior diameter of cylinder II a pair of suitable arcuate guides 42, 42 (Figs. 4 and 5) are welded in endwise spaced relation around the lower end of piston M, such associated members 42, 42 being slightly smaller in diameter than the inside of cylinder I I so that they may slide freely up and down in the cylinder.

Two suitable stop-pins 43, 43 are welded diametrically opposite each other in the wall of cylinder I I near the top of the same to limit the upward travel of piston 4I accomplished by the guide-members 42, 42 striking the stop-pins 43, 43 thus preventing further travel upwardly.

To enable the piston 4| to be properly introduced into the cylinder II such parts 42, 42 are spaced apart at two diametrically opposite points, at I42, I42, so that when inserting the piston 4| in the cylinder I I the piston is rotated until the gaps I42, I42 between the elements 42, 42 are in line with the stop-pins 43, 43, the piston 4| then being entered into the cylinder I I until the curved parts 42, 42 are below the stop-pins 43, 43, after which the piston is rotated which is its normal operating relation as shown in Figure 5.

Referring to Figure 4, it will be noted that the lower end of piston M is closed by a welded-in lower head 44 having an upwardly extended skirt 45 to which is welded a cover-plate 46 forming a hollow enclosure 41.

At its upper end piston M has welded thereon a ring 48 (Fig. 4) having an inwardly extended flange portion to which ring is secured by a plurality of screws 50, 59 a head 49, such united parts 48 and 49 constituting a closure for the top of the piston, the construction being sealed airtight by a suitable gasket 5| between the elements 48 and 49, the latter having an aperture therethrough normally closed by a filler plug 52 permitting pouring of oil into the inside of the piston after which is accomplished, of course, the plug is screwed in tight.

As is clearly portrayed in Figure 4, between the cylinder II and the piston M a suitable conventional packing is provided at 53 with its customary retaining gland 54 whereby the piston may move vertically with relation to the encasing cylinder in pressure-tight manner.

Such upper head 49 on its underside is drilled partially through at 55 at a point in line with the center of the bushing 31 to receive the rounded end portion I56 of a square rod 56 which extends down through a square hole in the bushing 31 and may slide endwise through such hole when the bushing is rotated, it being noted that when the bushing .3!v is turned. 12118 .-.rdde56;is also irevolved alike amount in:.the;same direction.

A plug-valve -51 in .therlower head t44. .Qf" the piston ll has inner and outer ports:58 sand 59 respectively so .thattassuchvalveis irritated: the

is thereby also :turned, it: being. thus evident-that such valve maybe npened orsclosedsby'theazoperation of .rodgzz-zby means :of thezasuitable-handle :22 attached to its .upperiend at .the polntwhere itextends upward through guide 23.

Referring'now to valve-6ll ,1 .(Fig. 4) in -wall 46 of chamber '41. in thelower portion rof'piston l4l, it 'will be .observed that an upright, open-top,

crescent-shaped cup iii .(Figs. l, 4 and '6) is mounted in any approved'manneron such-valve, a rod 62being fixedly attached to the cup and extending upwardlytherefrom with its top-end pivotally associated with one end of 'a lever 63 fulcrumed at.'64, a counterweight 65 being-suspended from the opposite end of such lever 83, the fulcrum memberBG-terminating at its lower end ins, horizontally extending portion forming a guide for the stem 16! .ofthe counterweight-65.

The weight value of suchcounterweight"65 is such that when the cup 6lis'full of oil and completely surrounded by oil the combined weights of the cup 61 and theattache'd valve -Sllandrod 62 are lighter thanrthe counterweight and; therefore, valve 60, shown closed in thedrawin is normally open when surroundedby oil.

However, when cup 6 1- is surrounded byair only the Weight value of the cup 6 I; which is full of oil, the attached valve 50 and'rod' iiz is great-erthan the weight value of the-counterweightit and consequently the cup full "of oil and associated parts will descend-and the valvefijil willclose.

Downwardlyextending tapered ribs 68 m valve 6% serve as a guide for the valve thus insuring. that it will always enterits seatjfiB,there-byclosing properly.

Two diametrically oppositefivertical ribs '1-0, it (Figsil, 4 and 5)..are welded to theinside of ie hollow piston d l ,the casting .34; having a projecting portion "H gFigsB, .4- and :5). notchedat itsv endto slidingly engage one of; suchwribs '10, this casting, 3d being. alsov supplied with/a1 swinging arm '52 notched at its outer. enditozslidably cooperate withuthe other: oppositerib' HI.

By rocking arm lz upiinto place so that its notch engages rib t ll i the-end; portion: of v the arm .by which it is hingedtoithecasting 34-maybe shove-d endwise through itshole in the casting at the same time entering thesu-bstantiallyhorizontal portion of arm T'lzlinto thenotch 73 (Fig. 3) provided on the side of the-casting.

i2 .isrsecurely, firmly held i-n place'in operative position by: means of nut "I l shown in Figure 5 screwed thereon, this arrangement being to facilitate assembly of the parts.

This it should be apparentithat asthe piston moves up and down the guides"'l0,j1l:s1ide through their respective notches in the. stationaryextended portion 1 l of casting 3,4 andlinz the. .outer endof the rigidly attached arml'IZ, this arrange- ,its associated parts from turning about-avcrtical axis with respect to piston-M Referring again to valvetl'l iFig. v i), which is operated by rotation of the-square shaft-cured 58;, a downwardly projecting vertical-stem: Hi-is imounted concentric with the ,valve,,;,and:slidable on suchstem isa disci'l'ii held normallyzdown by a superposed coiled-spring Tl.

. As is shown, the inside of the lower end-of such plug-valve .5? is tapered, flaringdownwardlyiso that. its .bore is larger at itsextreme .lOWE-lYfil'ld than-at a point further up, and'thus, when theidisc it is in its uppermost position,v asshowninliigure i, there is more restriction to the-passageof L011 through the valve than when the disc :is in its extreme downward position .bearingagainst astep it! on the lower end efzthestern, and;byi proper choice of spring "lltherate of flow of oil mayibe restricted to a predetermined amount.

,Spring it always tends to maintain that-disc down in the widest ,open position .thereof;-the

oil flowing upward throughvalve 5'1 and through the ports 58 and 59, thevelocity oi the .oil tending to raise the disc thereby restricting the opening and thuscausingthe oil topass eta-slower rate,

Operation.-The manner of functioning ofthis novel apparatus is as follows, it being understood --that;the top end of the piston ti may be connected in any approved manner to any suitable means 86 for raising and'lowering a loadsuch, fol-instance, as a vehicle to be inspected or repaired although, of course, it will be readily understood that any suitable mechanism may be 'actuated by the movements of the traveling piston. Such hollow piston or plunger ti isfilled with oil or other appropriate liquid to a suitable height, as indicated at A in Figure 4.

. The cup iii attached to the counterweighted valve 6b is now full of oil and is completely suspended in oil, the valve of the counterweight-65 being-such that it more than balances the weight of thevalve E6, the cup 6! and the attachedro'dBZ, whereby valve fill will be in wide open position gthus admitting oil by gravity into the hollow chamber 'l' which becomes filled therewith, but

since valve 5? is closed none of such oil hasbeen permitted to leave the piston and enter the cylinder.

V/hen'it is desired to elevate-the load by the ascent of the piston the valve-controlled compressed-airpipe 2| being connected to the T1120 such valve is manually opened admitting airiunder appropriate pressure to the pipe'IQ, thence to the chamber t l, then through the tubefifi. and

the ports 79 of member (it to the space above the oil in the piston.

Rod 22 by means of its handle" 522 is'thenro- .tatedin the proper direction thus revolving the od Zfland crank-arms '25 audit and link'30, this rotation causing the square rod'56 .to b

:turned through the action of arms'32 and '39 and hollow piston M to flow through the open valve -60 into the chamber 41, throughvalveb'l-tothe space in the cylinder under thepiston or plunger :4! whereby the latter is caused to rise vertically,

and when this takes place the square rod"r56 rascendswith' the piston sliding endwise throughthe bushing 31.

.Conventional packing 8! is employed on. the lower head M of the pistondl, .suchpackingam inent being'provided' t prevent the :casi yn zand 25 itsassoc-iate'dretaining'means sliding vertically on the outside of tube 26 in pressure sealing relation as the piston rises.

In this connection it is to be noted that the casting 34 and its cooperating and associated elements do not rise with the piston since they are secured to the tube 26 which is in turn fastened at its lower end to the cylinder-head i2.

Since, however, the square rod 56 slides through the bushing 37 in the casting II the operation of the above description for opening the valve 57 may take place at any point in the rise of the piston, and it should be observed that the series of controls may be operated to close the valve 51 at any position of the plunger.

As previously outlined, valve 80 is normally open as long as it and its companion cup are submerged in oil, but should the oil level in the piston 4| become too low for any reason, as for example, insufiicient filling, leakage, etc., so that as the piston H rises the oil level descends to a point near the bottom of cup 61, as indicated at B (Fig. 4) the cup will descend due to the lack of bouyant effect of surrounding oil whereupon valve 60 will thereby automatically close and thus halt further ascent of the piston 4 i.

This action is desirable, since, if air were to be admitted to the space below tthe piston, its action becomes erratic, ascending or descending by jerks instead of smoothly and evenl as is the case when supported entirely on oil. the latter being practically noncompressible.

The lowering of the piston and the load therein is accomplished by exhausting the air from the space above the oil in the piston through manipulation of the air-controlled valve i2! leaving such space open to the atmosphere.

Obviously, during such operation the oil in the cylinder flows back into the piston ready for the next lifting action. That is to say, the operation of the rod 22 opens valve 51, as described above permitting the oil to flow from the space below the piston in a reverse direction through valve 51 into chamber i! and thence through valve 60 into the hollow piston.

As previously presented, during such action disc 16 will tend to rise thereby restricting the return of flow of the oil upwardly through valve should the piston descend too rapidly due to a heavy load upon it.

Disc 76 under these circumstances will compress the spring I'l more with a heavy load on the piston than with a light load due to the greater oil velocity with the heavier load.

Naturally, by proper choice of disc size inside the taper of valve-plug '57 and of the strength of the spring H the rate of descent of the piston 4| may be automatically controlled within safe limits for any amount of load.

From what precedes, it should be clear that if valve 51 is manually closed during any movement of the piston such piston travel is immediately terminated and locked regardless of whether the air pressure is on or off.

Stated somewhat otherwise, it is to be understood that such valve 51 may be instantly closed at an point in the stroke of the piston without exhausting the air pressure, thus making it possible to stop the piston movement at once and not allow expanding air to continue to raise the piston when the air supply is shut off Those acquainted with this art will readily understand that this invention is not necessarily limited or restricted to the precise or exact details of structure and operation set forth and that reasonable modifications may be availed of with 8 out departure from the heart and essence of the invention and without loss or sacrifice of any of its material benefits and advantages.

I claim:

1. In a load lifting and lowering appliance of known general type having an upstanding cylinder accommodating a hollow piston with a pressure-seal between them allowing the piston to reciprocate in the cylinder, said piston being adapted to contain a liquid, and means to apply such liquid under pressure from the piston to the cylinder beneath the piston to raise the latter and to return the liquid to the interior of the piston to lower the latter, the novel combination of means providing an air-chamber below the bottom wall of the cylinder, means providing a liquid-chamber in the lower portion of the piston, a first valve connecting the interior of the piston with the liquid-chamber, a second valve connecting the liquid-chamber with the cylinder beneath the piston, a first upstanding stationary air-tube outside of the cylinder and connected at its lower end to the air-chamber, a second upstanding stationary air-tube in the piston extending down through the bottom walls of the piston and cylinder with its lower end in communication with the air-chamber and with its upper end in communication with the piston above the highest liquid-level therein, controllable means near the top of the first air-tube to admit air under pressure into the first air-tube and cause it to discharge from the second airtube into the piston or to discharge air from the first air-tube to the atmosphere, a first manually rockable rod occupying the first air-tube, a second rotary rod occupying the second air-tube, means operatively connecting together lower exposed portions of the two rods, and means connecting the upper portion of the second rod with the second valve to open and close the latter upon turning of the second rod by the manual turning of the first rod.

2. The novel combination presented in claim 1, including additionally in said combination a member mounted on the upper end of said second air-tube, longitudinal guide means on the inner face of said piston in sliding engagement with said member preventing turning of such member relative to said piston, and in which said means connecting the upper portion of said second rod with said second valve includes a bushing oscillatory in said member, a third upstanding rod slidable only through said bushing, and means connecting the lower end of said third rod with said second valve, whereby the piston and third rod may rise and descend while said member remains stationary.

3. The novel combination set forth in claim 1, including in said combination a supplemental valve in series relation with said second valve and spring-pressed toward open relation and acted upon by the liquid flowing upwardly through it against the action of such spring toward more closed relation.

4. The novel combination set forth in claim 1, including in addition in said combination liquidlevel controlled means in said piston maintaining said first valve open so long as the liquid-level in the piston is above a predetermined height and closing said first valve when such level falls below such predetermined height thus precluding unintentional escape of air from the piston, said means including an open-top cup attached to said first valve, an upwardly extended rod fixed to said cup, and counterweight means acting on said rod of a value suflicient to open and close such valve as specified prefatorily in this claim; a pressure seal in the bottom portion of the reciprocatory piston surrounding and in sealing engagement with said stationary second airtube the latter being coaxial with said piston; a member mounted on the upper end of said second air-tube, longitudinal guide-means on the inner face of said piston in sliding engagement with said member preventing turning of such member relative to said piston, and in which construction the means connecting the upper portion of the second rod with the second valve includes a bushing oscillatory in said member, a third upstanding rod slidable lengthwise only through such bushing but rockable with the bushing, and means connecting the lower end of said third rod with said second valve, whereby the piston and third rod may rise and descend while said member remains stationary; and a supplemental slidable disc-valve occupying a converging discharge-passage of said second valve and spring pressed toward the largest portion of said passage and also pressed by the liquid fiowing through such passage toward its smallest portion.

5. The novel combination set forth in Claim 1, including in addition in said combination liquidlevel controlled means in said piston maintaining said first valve open so long as the liquid-level in the piston is above a predetermined height and closing said first valve when such level falls below such predetermined height thus precluding unintentional escape of air from the piston, said liquid-level controlling means for said first valve including an open-top cup in the piston attached to said first valve, an upwardly extended rod in the piston fixed to said cup, and. counterweight means in the piston acting on said rod of a value sufiicient to open and close such valve as specified prefatorily in this claim.

6. In a load lifting and lowering appliance of known general type having an upstanding cylinder accommodating a hollow piston with a pressure-seal between them allowing the piston to reciprocate in the cylinder, said piston being adapted to contain a liquid, and means to apply such liquid under pressure from the piston to the cylinder beneath the piston to raise the latter and to return the liquid to the interior-of the piston to lower the latter, the novel combination of means providing an air-chamber below the bottom, wall of the cylinder, means providing a liquid-chamber in the lower portion of the piston, a first valve connecting the interior of the piston with the liquid-chamber, a second valve connecting the liquid-chamber with the cylinder beneath the piston, a first upstanding stationary air-tube outside of the cylinder and connecting at its lower end with the air-chamber, a second upstanding stationary air-tube in the piston extending down through the bottom Walls of the piston and cylinder with its lower end in communication with the air-chamber and with its upper end in communication with the piston above the highest liquid level therein, controllable means near the top of the first air-tube to admit air under pressure into the first airtube and cause it to discharge from the second air-tube into the piston or to discharge air from the first air-tube to the atmosphere, manually operable means occupying said first air-tube, said second air-tube and said air-chamber to open and close said second valve.

IRA A. WEAVER.

REFERENCES CITED The following references are of record in the of this patent:

UNITED STATES PATENTS Number Name Date 1,098,157 Koken May 26, 1914 1,864,325 Steedman June 21, 1932 2,336,817 Thompson Dec. 14, 1943 2,402,265 Thompson June 18, 1946 

